As we're shown ancient cave paintings discovered by Monarch depicting Godzilla, Mothra, Rodan, and King Ghidorah with one last one showing a stand off between Godzilla and King Ghidorah.

Though I'm curious if Kong is going to be in the rumble as well. Considering that Legendary has already confirmed that they're making a King Kong VS Godzilla maybe Kong will take on the roll of Anguirus as a one time enemy turned closest bash buddy to Godzilla.

I hope that happens, my inner child is already bouncing off the walls as it is